How to Fix mdnsNSP.dll Blocked from Loading in Windows 11

Immediate Diagnosis

If you see a notification from the Program Compatibility Assistant stating that mdnsNSP.dll is blocked from loading into the Local Security Authority (LSA), your system is likely running Windows 11 version 24H2 or later. This version enables LSA protection by default to prevent unauthorized code from accessing sensitive credential information.


The file in question, mdnsNSP.dll, is a component of the Bonjour service, which is often installed alongside Apple software like iTunes. Windows blocks it because the module is not digitally signed or recognized as trusted for the high-security LSA process. This is a result of Windows security features and not a failure of the Bonjour service itself.

Safest Fixes

1. Uninstall Bonjour if Not Needed

For many users, the Bonjour service is a remnant of an old iTunes installation or printer software that is no longer in use. If you do not use AirPrint or local Apple device discovery, removing the service is the cleanest solution.

  • Open Settings and navigate to Apps > Installed Apps.
  • Search for Bonjour in the list.
  • Click the three dots and select Uninstall.

2. Update iTunes and Apple Software

If you still use iTunes to sync devices, ensure you are running the latest version. Newer versions may include updated modules that comply with modern Windows security standards.

  • If you installed iTunes via the Microsoft Store, check for updates in the Store library.
  • If you used a standalone installer, open iTunes and go to Help > Check for Updates.

What Not to Do

Do not attempt to disable Local Security Authority (LSA) protection in your Core Isolation settings. While disabling this feature would stop the error message, it significantly reduces your system's security by leaving your login credentials more vulnerable to attacks. Security experts recommend keeping LSA protection enabled to maintain the integrity of the operating system.

When to Contact Official Support

If the Bonjour service is required for critical third-party networking tools and updating the software does not resolve the block, you should contact the software vendor's support team. They may need to provide a signed version of the DLL that is compatible with Windows 11 security features. You can find community discussions regarding this issue at the Apple Community or Microsoft Q&A.

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